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Commit 842b593c authored by Steven Moreland's avatar Steven Moreland
Browse files

binder_parcel_fuzzer: use FuzzedDataProvider 

This makes the code a little more readable and paves the way for having
more complicated Parcel creation.

As a side effect, this allows the number of instructions to be run on a
parcel to be larger than the size of the parcel itself, so we should
increase meaningful coverage for small parcel sizes.

Bug: N/A
Test: binder_parcel_fuzzer for several minutes
Change-Id: I30a8f6c40e5255b3d01b2bacc52990cfb50150f0
parent 354a51c8

libs/binder/fuzzer/main.cpp

+33 −49
Original line number Diff line number Diff line
@@ -21,15 +21,25 @@ 
#include "util.h"



#include <android-base/logging.h>

#include <fuzzer/FuzzedDataProvider.h>



#include <cstdlib>

#include <ctime>



template <typename P>

void doFuzz(

        const std::vector<ParcelRead<P>>& reads,

        const std::vector<uint8_t>& input,

        const std::vector<uint8_t>& instructions) {

void doFuzz(const char* backend, const std::vector<ParcelRead<P>>& reads,

            FuzzedDataProvider* provider) {

    // Allow some majority of the bytes to be dedicated to telling us what to

    // do. The fixed value added here represents that we want to test doing a

    // lot of 'instructions' even on really short parcels.

    size_t maxInstructions = 20 + (provider->remaining_bytes() * 2 / 3);

    // but don't always use that many instructions. We want to allow the fuzzer

    // to explore large parcels with few instructions if it wants to.

    std::vector<uint8_t> instructions = provider->ConsumeBytes<uint8_t>(

            provider->ConsumeIntegralInRange<size_t>(0, maxInstructions));



    // TODO: generate 'objects' data

    std::vector<uint8_t> input = provider->ConsumeRemainingBytes<uint8_t>();



    P p;

    p.setData(input.data(), input.size());
@@ -37,7 +47,11 @@ void doFuzz( 
    // since we are only using a byte to index

    CHECK(reads.size() <= 255) << reads.size();



    for (size_t i = 0; i < instructions.size() - 1; i += 2) {

    FUZZ_LOG() << "backend: " << backend;

    FUZZ_LOG() << "input: " << hexString(input);

    FUZZ_LOG() << "instructions: " << hexString(instructions);



    for (size_t i = 0; i + 1 < instructions.size(); i += 2) {

        uint8_t a = instructions[i];

        uint8_t readIdx = a % reads.size();
@@ -53,58 +67,28 @@ void doFuzz( 
    }

}



void fuzz(uint8_t options, const std::vector<uint8_t>& input, const std::vector<uint8_t>& instructions) {

    uint8_t parcelType = options & 0x3;



    switch (parcelType) {

        case 0x0:

            doFuzz<::android::hardware::Parcel>(HWBINDER_PARCEL_READ_FUNCTIONS, input,

                                                instructions);

            break;

        case 0x1:

            doFuzz<::android::Parcel>(BINDER_PARCEL_READ_FUNCTIONS, input, instructions);

            break;

        case 0x2:

            doFuzz<NdkParcelAdapter>(BINDER_NDK_PARCEL_READ_FUNCTIONS, input, instructions);

            break;

        case 0x3:

            /*reserved for future use*/

            break;

        default:

            LOG_ALWAYS_FATAL("unknown parcel type %d", static_cast<int>(parcelType));

    }

}



extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {

    if (size <= 1) return 0;  // no use



    // avoid timeouts, see b/142617274, b/142473153

    if (size > 50000) return 0;



    uint8_t options = *data;

    data++;

    size--;



    // TODO: generate 'objects' data



    // data to fill out parcel

    size_t inputLen = size / 2;

    std::vector<uint8_t> input(data, data + inputLen);

    data += inputLen;

    size -= inputLen;

    FuzzedDataProvider provider = FuzzedDataProvider(data, size);



    // data to use to determine what to do

    size_t instructionLen = size;

    std::vector<uint8_t> instructions(data, data + instructionLen);

    data += instructionLen;

    size -= instructionLen;

    const std::function<void(FuzzedDataProvider*)> fuzzBackend[3] = {

            [](FuzzedDataProvider* provider) {

                doFuzz<::android::hardware::Parcel>("hwbinder", HWBINDER_PARCEL_READ_FUNCTIONS,

                                                    provider);

            },

            [](FuzzedDataProvider* provider) {

                doFuzz<::android::Parcel>("binder", BINDER_PARCEL_READ_FUNCTIONS, provider);

            },

            [](FuzzedDataProvider* provider) {

                doFuzz<NdkParcelAdapter>("binder_ndk", BINDER_NDK_PARCEL_READ_FUNCTIONS, provider);

            },

    };



    CHECK(size == 0) << "size: " << size;



    FUZZ_LOG() << "options: " << (int)options << " inputLen: " << inputLen << " instructionLen: " << instructionLen;

    FUZZ_LOG() << "input: " << hexString(input);

    FUZZ_LOG() << "instructions: " << hexString(instructions);

    provider.PickValueInArray(fuzzBackend)(&provider);



    fuzz(options, input, instructions);

    return 0;

}